This invention relates to a method and a system for monitoring and characterizing a person's heart condition with respect to identifying different components of cardiac disease. Additionally, it relates to such a method and system wherein results from monitoring and characterizing activities can be employed for a number of purposes, including (a) diagnosis, (b) the creation of various kinds of currently useful and archival records, such as chart and electronic database records, and for (c) implementing various kinds of selectable control functions, such as controlling the operational behavior of a device like a pacemaker, and other.
In a sense, the present invention rests on an underlying concept which recognizes the special utility of gathering heart acoustical sounds (PCG modality) along with ECG data (ECG modality), and then measuring, evaluating and inter- and cross-relating and combining various components of these two kinds of data for the purpose of assessing various kinds of heart conditions. To simplify the concepts of inter- and cross-relating and combining will be understood to mean all such forms of sound/sound, ECG/ECG, sound/ECG, and ECG/sound data exploration.
As far as we are able to determine, where, in prior art practice, practitioners have gathered heart acoustical data, i.e., heart sounds along with ECG data (signatures), it has usually been the case that the heart-sound data is employed essentially only for various data timing purposes. In other words, we are unaware of any prior art proposal for gathering correlatable heart sounds and ECG data, and then processing these two kinds of data to develop a new kind of view into the status and behavior of a person's heart. A part of the underlying concept of this invention relates to locating and using features that are found in ECG information, along with features found in acoustic information, to improve understanding and diagnosis of the condition of a person's heart. It also recognizes the fact that these two kinds of data can be thought of as being “orthogonal” with respect to one another—“orthogonal” in the sense that they operate with relevance in different physical realms of heart activity. In this context, each of these two kinds of data can be characterized as possessing both “strengths and weaknesses” with respect to furnishing useful and important heart information. They are, in a sense, capable, when examined carefully, of providing very useful “complementary” information about heart condition. To deal with this situation, the invention, effectively, can be thought of as using the “strengths” contributed by one of these two kinds of data to “buttress the weaknesses” in the other kind of data, and vise versa. This, of course, is merely a stylized way of envisioning the “complementary” capabilities of these two data areas.
As will be well understood by those skilled in the art, heart sounds and heart ECG information each effectively takes a look at, or provides information about, different aspects of the heart. Respecting ECG information, the electrical activity of the heart is observed. This information, for example, gives data relevant to the health of cells, to characteristics of conduction pathways and speeds in the heart, and to various physical changes in the heart that are known to affect electrical heart activity. Other well known factors are also recognizably associated with ECG information.
Heart acoustic information looks primarily at physical mechanical and hydraulic properties of the heart (and of its chambers and valves), of blood, and of related vasculature.
Many cardiac conditions affect both the electrical and the acoustic signatures of the heart, and as will be seen, this invention makes unique use of possibilities for measuring, evaluating and relating and combining information drawn from these signatures to enhance heart-condition monitoring and assessment.
As brief illustrations of the promise and power of combing acoustical and electrical heart signatures, it is well known that the presence of the abnormal diastolic S4 or S3 heart sounds increases the odds of a correct determination that the associated person has ischemia—one important aspect or component of heart disease. When information relating to these abnormal heart sounds is combined with ECG information, a decidedly better diagnosis and interpretation relative to ischemia is possible.
Another example involves the fact that the S4 heart sound generally indicates a stiff left ventricle. As such, this increases the odds of either the existence of a prior myocardial infarct (PMI), or the presence of Left Ventricular Hypertrophy (LVH).
Further generally describing the present invention in the setting of its prior art landscape, heart sounds are acoustic phenomenon that are created due to vibrations within the heart and its structures. These vibrations have characteristics that are unique to an individual—characteristics such as the size of the heart chamber and the thickness of its walls, as well as variations within an individual due to dynamic changes in the heart's mechanical properties, such as transient increased stiffness of the ventricle. The unique characteristics of a person's heart sounds, for example, characteristics of the time-based waveforms representing such sounds, can be “fingerprinted”, or captured, by a variety of measurements and parameters, and then used in a number of important ways.
If the hemodynamic condition of an individual, and of that individual's heart properties, remains constant, then one would expect that the associated heart-sound waveforms and the associated fingerprint(s) would remain relatively constant. The acoustic waveforms and fingerprints for an individual that demonstrate change over time would indicate a change in the mechanical properties of the heart, and/or in the hemodynamic state of individual per se. For example, if an individual experiences a transitory ischemic condition that causes increased stiffness of the left ventricle, along with increased left ventricular end diastolic pressure, one would expect an abnormal heart sound, such as an S3 or S4 heart sound, to develop. Aside from noting a new development of abnormal heart sounds, changes in specific parameters can be useful when one is evaluating change in a person. As an illustration, the acoustic fingerprint could be used to quantitate the amplitude of the normal S1 heart sound during exercise, with the expectation that a healthy individual would display increased amplitude, with the lack of an increased amplitude being interpretable as a sign of disease.
Another area of interest involves quantitating changes that take place during the administration of drug therapy to a patient. To illustrate this, it is common to treat heart-failure patients with diuretics, and it would be expected that the acoustic fingerprint in a patient undergoing treatment with diuretics would change as the hemodynamic state of that person changed.
Beside the utility of employing such a fingerprint for tracking changes in the same individual, such a fingerprint could be used in a comparison with a “normal” fingerprint for a particular selected population. Thus, to assist in diagnosis of left ventricular dysfunction, the fingerprint of an individual with altered left ventricular mechanical properties could be compared to the fingerprint for a non-diseased population in the same age range, and the differences in these fingerprints could be used to assist in the diagnosis of the presence of left ventricular dysfunction.
The process of creating an acoustic fingerprint for an individual, generally speaking, consists of a acquiring a person's acoustic heart sound data (signature) along with ECG data (signature), processing the heart-sound data to detect particular waveform components, and then quantitating various parameters and measurements. A list of parameters and measurements that might make up a fingerprint include (a) durations of the various heart sounds, S1, S2, S3 and S4, (b) amplitudes of these heart sounds, (c) relative amplitudes of the same heart sounds, for example, S1/S4 ratio, (d) timing relationships among the heart sounds, for example the S4 to S1 heart sound interval, (e) timing relationships between heart sound components and ECG data, for example, Q onset to S1 interval, (f) frequency composition of heart sounds (i.e., energy plots of the whole acoustic waveform or of any of its sub-components), (g) presence of abnormal heart sounds, including the presence of murmurs and stenosis, (h) multi-parameter “spaces”, such as the relationship of PR interval to S4 interval, and many more.
The detailed description of the invention which now shortly follows will more fully amplify these various considerations and advantages associated with acquiring and correlating acoustic and electrical heart signatures. It will also disclose other features and advantages of the invention in categories which will become quite clear to those generally skilled in this art.